In the field of satellite communications, obtaining a high-quality communication involves particular performance for the electromagnetic waves produced by the antenna structure used in the communication in terms of gain and secondary lobe level (ratio between the intensity of the secondary lobes and the intensity of the primary lobe). This is even more true for so-called “broadband” satellite communications, i.e., not emitting only voice.
In the particular case of the Ka electromagnetic band, two separate frequency bands are involved. In fact, in emitting, the electromagnetic waves of the Ka band have a frequency comprised between 27 gigahertz (GHz) and 31 GHz, while in receiving, the electric waves of the Ka band have a frequency comprised between 17.3 GHz and 21.2 GHz. In the rest of the description, the Ka band for emitting is denoted Tx, while the Ka band for receiving is denoted Rx. Furthermore, the polarizations of the emitting and receiving waves are generally of the circular type, and may or may not be opposite.
These frequencies and these circular polarizations in receiving and emitting impose constraints on the antenna structure. Furthermore, in the context of satellite connections, the antenna should be oriented so as to aim at the satellite making it possible to establish the connection. Furthermore, to reduce the visual signature (physical bulk), parabolic antenna-type solutions are generally not favored. This is particularly true given that in that case, the depth of the antenna is constrained by the focal distance of the source illuminating the satellite dish.
Among the antenna structures making it possible to respect these various constraints, it is known to use an electronically-scanned antenna for the emitting of a wave whose central frequency is around 30 GHz and for the receiving of a wave centered around 20 GHz.
However, the electronically-scanned antenna obtained may have a significant bulk corresponding to the radiating surfaces of each of the operating modes (emitting/receiving). Furthermore, the efficiency of such an antenna may be insufficient based on the elementary antenna used and the associated power circuit, in particular when patch-type antennas are involved.
Furthermore, the implementation of a circular polarization in a first direction in the emitting part and a circular polarization in a second direction that may or may not be opposite the first direction for the receiving part proves difficult if a polarizer is used, which reduces the usage flexibility of the considered scanning antenna.